FIELD OF INVENTION:
The present invention is directed to a low cost, on-line contact-less automatic method and system for sensing and reducing the amount of cobbles by means of microprocessor based control on different shears in four strand rolling mills from billet to wire rods, involving photosensors, at selective locations. The sensing of metal/cobble is carried out by couple of photosensors located in selective positions in each strand. The photosensor based control is provided in roughing and the intermediate stand for sensing the cobbles in narrowly spaced four strands of the wire rod mill of steel plants. But in the finishing stands the metal remains enveloped by black colored water therefore said photosensor based detection and control on metal cobble cannot be applied their; suitable electrical sensors to sense the variation in the load current of rolling stand motor due to arrival of metal/cobble is utilized for sensing the rolling of metal through that particular rolling stand. However, load current variation method is not suitable in the roughing and intermediate stands of rolling mills since four and double strands rolling is carried out by respective single motor. The system also provides for a control regarding immediate action in the event of detection of cobble at any particular stand to prevent further accumulation of cobbled metal in narrowly spaced different strands. Low cost photosensors and rolling motor load current detecting electrical sensors are selectively used to scan the entire four strand mill The system also ensures by timely and selectively deploying the different types of shears at various locations in the rolling mill, the amount of cobble is minimized such that the waste/scrap is reduced and mill availability is increased and also the production is increased resultantly by about 4%. The pay back for the cost of installation is less than a week Thus the present system of detecting and reducing the amount of metal cobble in rolling mill strands and effectively controlling by means of microprocessor adaptively deploying selective shears, ensuring safety of operators has high potential for industrial application and economic advantage.
BACKGROUND AND PRIOR ART:
It is well known in the art of steel rolling mills for conversion of billets to wire rods in successive rolling stands in various rolling strands that the formation of cobble is a problem causing loss of production due to downtime at the different stages of the rolling mills. This in turn, causes wastage of rolled sections at either of the roughing, intermediate or finishing stages of the mills. Moreover, such unpredictable occurrences of metal cobbles also endanger the operators' working interface with said rolling mills due to the risk of flying cobbles hitting at high speeds causing fatal injury. The detection of such cobbles in any of the rolling strands in any of the stages is very difficult to be detected by the operator.
2

Because that the operator is unable to continuously scan the entire group of stands covering about 30 meter long area in order to detect the exact location of occurrence of the cobble and thereby operating the adjacent shear to discontinue the cobble accumulation in that location. Moreover, operating any shear neighboring to a rolling strand, by mistake due to wrong anticipatory identification of location of cobble, fresh defect free metal is cut and destroyed and thereby adversely affecting productivity and costs.
The nature of problems related to occurrence of cobble and difficulty in their identification is different in nature from one stage to another due to the uniqueness of construction and operation of a particular section/ group of stands. In intermediate stands for example, two strands are located very closely, say separated by 15mm only. In case of occurrence of cobble, in between any of these rolling stands, it is extremely difficult to identify the particular strand in which the cobble actually has taken place. This leads to operating a shear adjacent to any of the strands by the operator by mistake/confusion and thereby damaging/destroying healthy material completely that recur on many such occasions.
In the finishing stands, there is the possibility that the high velocity flying cobble may hit the operator therefore the finishing stands are surrounded by the metallic cage. The high power de-scaling pumps further increase the noise level thereby operators are unable to listen the sound generated due to occurrence of cobble.
No method or system for detection and control of occurrence of cobble in rolling operations as of the present invention in the related area were disclosed on the internet based web search or in any of the earlier publications in leading journals like IEEE or IFAC etc.
The cobbles can also occur in the big looper area at the end of the first intermediate stands for four strands rolling or it can also occur at the small looper area at the end of the second intermediate stand for two strands rolling. Either of these occurrences are difficult to control. Whenever cobble occurs in big looper area, the operator cannot distinguish the region where cobble has occurred. Due to poor visibility, he simply operates the Double Strand Snap Shear (DSSS) so that the incoming healthy metal falls in the bigger looper pit thereby it increases the further burden for removing the metal because two strands are spaced very closely and not isolated with each other and affects rolling of neighboring stands. While in small looper area their spacing increases gradually up to 2 m. The metal which is under tension in the small looper as well as in the big looper area is accumulated
3

in the second and first intermediate groups respectively and leads to stoppage of mill at least for 15 minutes. The time required for detecting the occurrence of a cobble and the time needed to remove the cobble is different in different section and is substantially high in magnitude following the conventional methods. There was no such method available that could detect the location of occurrence of cobble in any of the rolling stands and facilitate their removal or control the accumulation.
There was thus a continuous need for developing an automatic system for detecting specific location of occurrence of cobble in rolled metal in any of the sections of a rolling mills for converting billets to wire/rods through successive rolling stands and arrest accumulation of cobble automatically by operating appropriate shears at right time, and thereby ensure safety, higher productivity and economy in rolling operations.
OBJECTS OF THE INVENTION:
The basic object of the present invention is therefore directed to develop an on-line contact-less automatic system for sensing the cobbles in narrowly spaced strands of wire rod mill of steel plant and reducing the amount of cobble in different stands in wire rod mills by providing appropriate type of sensors at selective location at each of the stands that are operatively connected to a microprocessor for detection of specific location of cobble and controlling the shears of various type at desired locations to discontinue the accumulation of cobble in a safe and accurate manner and there by reduce scrap, improve productivity at less cost.
A further object of the present invention is to ensure detection of exact location of cobble in any of the rolling stands by deploying appropriate sensor means either photosensor or motor load current sensor for proper detection depending on working conditions in the said stands.
A still further object of the present invention is to detect and control the cobble in wire rod mill in steel plant selectively involving sixteen numbers of low cost photosensors for the different rolling stands where the narrowly spaced strands as low as only 15mm apart and its spacing gradually increases; and four numbers of electrical sensors for sensing rolling motor load current variation at the finishing stands where the photosensors are unable to detect metal cobble, being covered under the envelop of black colored water/steam.
4

A further object of the present invention is to provide a microprocessor based control/program that detects the input relating to instance of occurrence of cobble through said sensors and send appropriate command/signal to operate a particular shear out of twelve numbers provided at selective locations at different rolling stands to stop further accumulation of cobble in any of the rolled metal strand/s where the cobble has been detected.
Yet another object of the present invention is directed to reduce time required for detection of cobble and the time taken for its removal from the main rolling line, by said microprocessor controlled faster method, eliminating/reducing requirement of conventional oxy-acetylene gas cutting for such purpose.
A further object of the present invention is to reduce operator's fatigue by eliminating manual anticipatory detection of cobble by scanning the entire 30 meter long rolling area and its control in the intermediate and finishing stands for four strands and two strands rolling, ensuring safety of the operator in said automatic system.
A still further object of the present invention is to reduce the rolling mill downtime for detection and removal of cobble once occurred and thereby increasing production (and productivity) by about 4%.
Yet another object of the present invention is to minimize the defective/cobbled rolled material at any of the rolling stages and also to avoid the cutting of healthy metal in neighbouring strands by manual mistake in detection by the operator.
A further object of the present invention is to ensure the economic gain in terms of economizing rolling operation by reducing the amount of metal during occurrence of cobble such that the pay back for the cost of installation of the system is less than even a week.
Another object of the present invention is to generate data/report covering information about number of cobbles occurred per hour/shift in different groups of particular strand; the automatic system of cobble detection and control, also provide mimic diagram at one place for metal flow/cobble/shear operation, for diagnosis purpose.
5

SUMMARY OF THE INVENTION:
The basic aspect of the present invention is therefore directed to developing an on-line contact-less automatic system for sensing the cobbles in narrowly spaced strands of wire rod mill of steel plant, in any of the rolling stands, by selective use of sensors and microprocessor based control to curb accumulation of cobble by operating selective shears on the cobbled metal strands, comprising:
photo sensor means for sensing the metal in the roughing and intermediate stands;
load current sensor means for sensing the variation in load current for sensing the metal in the finishing stand where the metal is enveloped including by black colored water;
microprocessor means adapted to detect instances of occurrence of cobble; and
control means for immediate corrective action to prevent further accumulation of cobbled metal in narrowly spaced different strands
A further aspect of the present invention directed to an on-line contact-less automatic system for sensing the cobbles in narrowly spaced different strands of wire rod mill of steel plant wherein at least 16 nos. of photo sensors and 4 nos. of rolling motor load current sensors have been used to achieve desired detection and control of metal cobble.
A further aspect of the present invention directed to an on-line contact-less automatic system for sensing the cobbles involves continuous sensing of metal flow using said photo sensors comprising providing ,
(i) said photo sensors at (a) 8 different points of four strands rolling;(b) 4 different points of double strands rolling;(c) 4 different points of single strand rolling stand; and (II) said motor load current sensors at single strand rolling.
A further aspect of the present invention directed to an on-line contact-less automatic system for sensing the cobbles in steel plants, said selective types, numbers and location of sensors adapted to scan and detect occurrence of cobble in any specific location in the
6

entire stretch of over 30 meter long rolling area, comprising 23 rolling stands in preferred groups through roughing, intermediate and finishing stages.
According to a preferred aspect of the present invention, the control strategy for controlling the amount of cobble in each of the stands and looper areas is adapted to install two photosensors at the entry and exit of each of such groups in respective areas and the operation of selective shears, either flying shears or double strand snap shear or a single strand snap shear, are effected to minimize the amount of cobble when the front of a metal does not come out within predetermined time which is sensed through end sensor for that group and is given as, T=fn (dn, Dn,Nn/ln, S),
Where dn are the different diameters of metal before entering into respective stands in mm, Dn are the different diameters of rolls in different rolling stands in mm, Nn speed of different roll in rpm, ln is distance between different rolling stand with respect to first rolling stand of the particular group S is the slip between metal and roll and it vanes 4-4.5% .
A further aspect of the present invention directed to an on-line contact-less automatic system for sensing the cobbles in narrowly spaced four strands of wire rod mill of steel plant, comprising:
controlling the amount of cobble in the finishing strand based on the status of the metal existing from the finishing strand is determined based on the variation in the load current (AL) is determined based on the difference of the armature current (IL) at load condition and no load current (Io) of the motor and if the status identified is indicative that the metal has not come out in predetermined time then single strand snap shear is activated; controlling the amount of cobble in a second intermediate strand comprising providing two photo sensors adapted to sense the metal at entry and exit of the group and if the front of metal does not come out in predetermined time then operating the double strand snap shear along with flying shear;
controlling the cobble for reducing the amount of cobble in the small looper area comprising providing two photo sensors adapted to sense the metal at entry and exit of the group and if the front of metal does not come out in predetermined time then operating only the flying shear;
A further aspect of the present invention directed to an on-line contact-less automatic system for sensing the cobbles in narrowly spaced four strands of wire rod mill of steel
7

plant, said microprocessor based automatic detection of location of occurrence of cobble and control of accumulation of cobble and to prevent from further carry forward of the same in succeeding stands is favored by shearing said cobbled metal strand by operating selective neighboring shear to a specific strand at any stage, said different types of shears being twelve in numbers operatively connected with and actuated by said processor depending on corresponding signal sensed by the sensors.
According to a further aspect of the present invention, said online contact-less automatic detection and control of amount of cobble in any of the metal strand minimizes scrap by quick and correct detection of cobble occurrence and initiating prompt shearing action such that the downtime of rolling mills is reduced and production increased by about 4%.
According to a further aspect of the present invention, said system for detection and control of cobble in any of rolled metal strands in four strand rolling mills, sense the front end metal that comes out within a predetermined time from the exit point of a group of rolls, in particular from the end point of the finishing stand ending at 23rd stand, such that the descaling pumps start automatically creating a cloud of steam /black colored fluid mass, thus making photosensors ineffective to sense light radiation from metal under this cloud and thus necessitating use of rolling motor load current sensor.
According to a further aspect of the present invention, detecting occurrence and amount of cobble and its control is exercised through a microcomputer consisting of Intel 8085-A 8 bit microprocessor, 2 KB EPROM, 2KB ROM 8355 for holding monitor software and application program and 2 nos. each of 512 kb static ram to hold the intermediate data for manipulation and subsequent outputtmg. Port A and port C of RAM 8155/0 and 8155/1 are used as input ports while port B are used as output ports. Output of the 16 numbers of photosensors, 4 numbers current sensors, 1 way 6 poles selecting switch are connected with port A and port C. The control driving circuit of all the 12 numbers shears is connected to port B of each chip through opto-coupler MCT2. The output of optocoupler is fed to n-p-n transistor for driving the 12V relay The NO(normally Open) contact of 12 V relay is used to controlling the coil supply of 230 V AC relay. The potential free contact of 230 V AC relay is connected to control circuit of shears.
8

According to a further aspect of the present invention said sensor and microprocessor based control of metal cobble in rolling strands is achieved being interfaced wtth software means comprising:
Registers B, C, D, and E of Intel 8085-A is used for storing the rolling numbers that corresponds to rolling time of a metal in strand A, B,C and D respectively;
The predetermined time for metal to pass from entry to exit in a group of rolling stands at any stage is obtained once metal is sensed by photo-sensor PS 16 of any strand at entry, the current rolling number which is stored in register B is subtracted from reference number that represent the normal rolling time between PS-16 to PS-19,
The control on appropriate shear is initiated when the status of PS-19 is sensed and after predetermined time status is sensed and the particular metal strand does not reach before PS-19 i.e. when the resultant of accumulator goes to minus then processor senses the next rolling stand otherwise metal status before PS-19 is sensed.
The present invention and its objects and advantages are described in greater details with reference to accompanying figures and non-limiting illustrative examples.
BRIEF DESCRIPTION OF FIGURES:
Figure 1: Illustrates the location of different shears and sensors in wire rod mill according to the present invention.
Figure 2: Illustrates the lay out configuration of the microprocessor and its interface with different shears and sensors, according to the present invention
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURES:
Reference first invited to Figure 1, wherein the location of different shears and sensors in wire rod mill according to the present invention has been schematically illustrated; with reference to a particular embodiment for rolling of wire rods from billet sections, to describe the manner in which the present invention is implemented.
9

The wire rod mills in steel plants conventionally produce wire rods of different diameter say 6 mm, 8 mm and 10 mm of the length in the range of 3 Km, 2.3 Km,.1.8 Km respectively from 12 m long billets of 100 mm x 100 mm cross section by rolling through a number of successive stages of rolling earned out in 23 rolling stands. The said rolling stands/stages follow immediately after the continuous casting furnace generating l00mmx100mm billet sections on continuous basis.
The rolling mill is divided into following four groups comprising specified numbers of rolling stands, as illustrated in said figure 1. Appropriate shears, either flying shears(FS) or snap shears(SS), are installed at the entry position of each group. The billets are first made to pass through the roughing group/stands(RS) comprised of serial numbers 1 to 9 of rolling stands. The First intermediate group/stands(FIS) having serial numbers 10 to 15 of rolling stands, having flying shears located in between the roughing and the 1st intermediate groups. The Second intermediate group/stands (SIS) comprise of serial numbers 16 to 19 rolling stands having double strand snap shear (DSSS), located prior to entry of metal to this stands. The Big Looper is located in between stand 15 and stand 16. The finishing group/stands consist of rolling stands serial numbers 19 to 23 having single strand snap shear( SSSS ). The snap shear works on the principle of free fall of heavy body on the rolled metal and pneumatically controlled through solenoid Snap shears are operatively synchronized with Flying shear.
Different types of problems are involved in detection of the occurrence of cobble, in exiting operational procedure in the different stages, as detailed below.
In intermediate stands, two adjacent rolled metal strands are very closely spaced, say 15 mm apart. In case of occurrence of cobble, manual detection of the same by the operator is not feasible and the particular strand in which actual cobble takes place cannot be identified, in conventional method Any mistake by the operator to identify the exact location of occurrence of cobble leads to operating neighboring shear in a strand where cobble has not occurred and thereby healthy metal is destroyed completely. Secondly it is impossible to scan the metal continuously over 30 m long area in order to sense manually the occurrence of cobble.
In the existing practice, whenever cobble occurs in big looper area, the operator cannot distinguish the region where cobble has occurred. Due to poor visibility, he simply operates
10

the DSSS so that the incoming healthy metal falls in the bigger looper pit thereby it increases further the burden for removing the metal. Moreover the two strands being very closely spaced and do not isolated from each other and thus affecting rolling of neighboring stands. While in small looper area their spacing increases gradually up to 2 m.. The metal which is under tension in the small looper as well as in the big looper area is accumulated in the second and first intermediate groups respectively and leads to stoppage of mill at least for 15 minutes.
In the finishing stands, high velocity flying cobbles may hit the operators therefore the finishing stands are surrounded by the metallic cage. The high power de-scaling pumps further increase the noise level thereby operators are unable to listen the sound generated due to occurrence of cobble, creating further confusion in detection.
The present invention is directed to remove the limitations of the prevailing system as described above by incorporating means for detection and control of cobble in rolled metal strands at any of the stands. The invention make use of sixteen numbers of low cost photosensors(PS) and four numbers of rolling motor load Current Sensors(CS), selectively located for intended detection of cobble at any of the rolling stands and for any of the rolled metal strands and thereby activating/operating appropriate shears neighbouring to the particular strand to discontinue further accumulation of cobble or to stop carrying it further down the rolling line, once detected
Referring back to the figure 1, the detection of occurrence and automatic control of amount
of cobble, of the present invention are further described below:
The system comprise low cost, online contact-less sensing of cobbles in narrowly spaced four
rolling strands, covering all the four groups e.g. roughing group stands(RS)7 1st and 2nd
Intermediate group stands(FIS & SIS) and the finishing group stands(FS), through different
types of sensors which are selected to suit according to site condition. This is achieved by
continuous sensing of metal flow by using 16 numbers photo sensors and 4 numbers' motor
load current sensors, selectively located at the entry and exit points of metal from respective
groups of rolling stands in said four stages. The 16 numbers photosensors are located as
follows:
(i) At 8 different points of four strands of single rolling stand,(II) at 4 different points of two
strands of double rolling stand,(III) at 4 different points of single strand of single rolling
stand.
11

The strategies for achieving the necessary detection of occurrence of cobble and operating selective shears to control accumulation of the cobble, following the strategies as given below:
(a). Control strategy for reducing the amount of cobble in the finishing stands(FS): The flow of metal before and after finishing stands is sensed by two photosensors as shown in Fig- 1. If the front of metal does not come out from finishing stands in predetermined time, then SSSS is operated, while the predetermined time is given as follows:

Where dn are the different diameters of metal before entering into respective stands in mm, Dn are the different diameters of rolls in different rolling stands in mm, Nn speed of different roll in rpm, ln is distance between different rolling stand with respect to first rolling stand of the particular group. S is the slip between metal and roll and it varies from 4 to 4.5% .
As soon as front end of metal crosses last stand i.e.23rd stand, the de-scaling pump starts and entire finish rolling stand is enveloped by clouds of steam therefore the light/heat radiation of metal is unable to reach respective photo sensors. Owing to this limitations of site condition, photo sensors for continuous scanning of metal condition of single strand for detecting cobble at the finishing stage is not suitable; so proper detection of occurrence of cobble at finishing stage is achieved by rolling motor load current sensors sensing variation in the load current ALof rolling stand motor having the ratings of 350 KW, 1200 rpm, Field separately excited 220 VDC, Field current 2.4 Amp. The armature current is tapped by inserting current coil around the incoming bus bar of supply of thyrister converter of motor and the difference in armature currentis given by:

Where, ILand Io are the armature current and no load current of motor respectively.
(b) Control strategy for reducing the amount of cobble in the second intermediate
stands(SIS): Two photosensor have put to sense the metal at entry and exit of the group. If
the front of metal does not come out in predetermined time, then DSSS along with Flying
shear is operated to control the amount.
(c) Control strategy for reducing the amount of cobble in the Small looper area(SL) [: Two
photosensor have put to sense the metal at entry and exit of the group. If the front of metal
does not come out in predetermined time, then only Flying shear is operated
12

(d) Control strategy for reducing the amount of cobble in the big looper area : Two photosensors have put to sense the metal at entry and exit of the group. If the front of metal does not come out in predetermined time, then only Flying shear is operated.
Area of occurrence of cobble and operation of different respective shears for their control of accumulation are given in Table - A below: Table - A:

S No
Cobble in
Shear operation
1
#16 to # 19
DSSS + Flying shear
2
Small looper
Flying shear
3
#20 to # 23
SSSS + Flying shear
The details of sensing time of cobble and time needed to remove the cobble for different sections of mill for different diameters, as compared to the conventional manual method , the net saving in time as well as saving in amount/length of cobbled metal and also the reduction in the requirement of gas cutting, is given in Table B. Table B :

Group
Wire rod dia.
Time needed to detect the cobble
Length of cobble
Time needed to remove the cobble
Time saving
Nos. of places gas cutting needed

Manual
Auto
Manual
Auto
Man -ual
Auto

Manual
Auto
Finishing
6 mm
5 sec
0.4 sec
150
m
15 m
10 min
7 min
3 min
15 nos
3 nos

8
mm
5 sec
0.6 sec
135
m
18m
10 min
7 min
3 min
12 nos
2 nos

10 mm
6 sec
0.7 sec
105 m
14m
10 min
7 min
3 min
10 nos
2 nos
i
2nd Interme diate
6
mm
7 sec
0.9 sec

18m
10 min
5 min
5 min
12 nos
3 nos

8
mm
7 sec
1.1 sec
90m
20 m
10 min
5 min
5 min
11 nos
3 nos

10 mm
7 sec
1.3 sec
85m
17m
10 min
5 min
5 min
8 nos
4 nos
Big Looper
6
mm
7 sec
0.2 sec
62m
0m
15 min
0 min
15 min
10 nos
0 nos

8
mm
7 sec
0.3 sec
55m
0m
15 min
0 min
15 min
S nos
0
nos

10 mm
7 sec
0.4 sec
50 m
0m
15 min
0 min
15 min
G nos
0 nos

Reference is now invited to Figure 2 of the accompanying figures that illustrates the btock diagram of hardware configuration of microcomputer consisting of Intel 8085-A 8 bit microprocessor, 2 KB EPROM 8755, 2KB ROM 8355 for holding/storing monitor software and application program and 2 numbers each of 512 kb static RAM to hold/store the intermediate data for manipulation and subsequent outputting. Port A and port C of RAM 8155/0 and 8155/1 are used as Input ports while port B are used as output ports. Output of 16 numbers of photosensor, 4 numbers of current sensors and 1 way 6 poles selecting switch are connected with port A and port C. The control driving circuit of all the twelve numbers dffferent shears is connected to port B of each chip through opto-coupier MCT2.
Said microprocessor based automatic control of the present invention comprising selective use of photosensors and rolling motor current sensors/or control of rnetal ccibbje in rolling strands ,is achieved being interfaced with software means comprising:
Registers B, C, D, and E of Intel 8085-A is used for storing the rolling numbers that
corresponds to rolling time of a metal in .strand A, B,C and D respectively;"
The predetermined tirne'for rnetal to pass from entry to exit in a group of roiling stands at
any stage is obtained once metal is sensed by photo-sensor PS 16 of any strand at entry,
the current rolling number which is stored in register B is subtracted from reference number
that represent the normal rolling timebetweenPS-16 to PS19;
The location, of various- 20- numbers of different sensors( 16 numbers PS and 4 numbers, CS)
with respect to serial- number, of rolling stands- from 1 to 23 and the port connection, details
for the sensors as well as the 12 numbers various shears(DFSS,SSSS &FS) at respective
locations corresponding to four rolled strands( marked A,B,C,&D) are summarized in
accompanying, Table-1.
14

Table 1;

SL.
No-
Strand
Sensor
Chip-8155 /
Part/ Bit
1
A
PS 16
0
AO
2
A
PS 19
0
Al
3
A
PS 20
0
A2
4
A
PS 23
0
A3
5
A
CS23
0
A4
6
B
PS 16
0
A5
7
B
PS 19
0
A6
8
6
PS 20
0
A7
9
B
PS 23
0
CO
10
B
CS23
0
Cl
11
C
PS 16 _,
0
C2
•12-
c
PS 19
0
C3
13
C
PS 20
0
C4
14
C
PS 23
0
C5
15
C
CS23
1
AO
16
D
PS 16
1
Al
17
D
PS 19
1
A2
18
D
PS 20
1
A3
19
D
PS 23
1
A4
20
D
CS23
1
A5
21
A
DSSS
0
BO .
22
A
FLYING SHEAR
0
Bl
23
A
SSSS'
0
B2
24
&
DSSS
0
Bi
25
B
FLYING SHEAR
0
B4
26
B
SSSS
0
B5
27
c
DSSS
0
66
28
C
FLYING , SHEAR
0
B7 ,
29
c
SSSS
1
BO
30
D
OSSS
1
Bl
31
D
FLYING SHEAR
1
B2
32
D
SSSS
1
B3

15

WE CLAIM:
1. An on-line contact-less automatic system for sensing the cobbles in narrowly spaced
different strands of wire rod- mill of steel plant comprising:
photo sensor means for sensing the metal in the roughing and intermediate strands;
load current sensor means for sensing the variation in load current for sensing the metal in the finishing stand where the metal is enveloped including by black colored, water;
microprocessor means adapted to detect instances of occurrence of cobble; and
control means for immediate corrective action, to prevent accumulation of cobbled metal in narrowly spaced different strands.
2. An on-line contact-less automatic system for sensing the cobbles in narrowly spaced
different strands of wire rod mill of steel plant as claimed in claim 1 wherein there are 16
nos. of photo sensors and 4 nos. of load current sensors.
3. An online contac-less automatic system for sensing trie cobbles in narrowly spaced
different strands in various rolling stands of wire rod mill of steel plant as claimed in anyone
of claims 1 or 2 comprising:
continuous sensing of metal flow using said photo sensors comprising providing, (1) said photo sensors at (a) 8 different points of four strands of single rolling stand;(b) 4 different points of two strands of single rolling stand;(c) 4 different points of single strands of single rolling stand; and (ii) said motor load current sensors.
4. An on-line contact-less automatic system for sensing the cobbles in narrowly spaced
different strands of wire rod mill of steel plant as claimed in anyone of claims 1 to 3 wherein
said microprocessor means is adapted to detect the instances of occurrence of cobble and
operate particular shears out of 12 shears.
5. An on-line contact-less automatic system for sensing the cobbles in narrowly spaced four
strands of wire rod mill of steel plant as claimed in anyone of claims 1 to 4 comprising
16

means to generate reports about no. of cobbles per hour in different group of particular strands in hour/shift basis and its wastage in tonnage.
6. An on-line contact-less automatic system for sensing the cobbles in narrowly spaced four
strands of wire rod mill of steel plant as claimed in anyone of claims 1 to 5 comprising
means to provide complete mimic diagram selectively based on metal flow, cobble and
shear operation.
7. An on-line contact-tess automatic system for sensing the cobbles in narrowly spaced four
strands of wire rod mill of steel plant as claimed in anyone of claims 1 to 6 comprising
hardware configuration of 8 bit microprocessor.
8. An on-line contact-tess automatic system for sensing the cobbles in narrowly spaced four
strands of wire rod mill of steel plant as claimed in anyone of claims 1 to 7 comprising;
controlling the cobble in the finishing strand based on the status of the metal exiting from the finishing strand is determined based on the variation in the load current (AL) is determined based on the difference of the armature current (IL )and no load current (IQ) ,of the motor and if the status identified is indicative that the metal has not come out in predetermined time then single strand snap shear is activated;
controlling the cobble in a second intermediate strand comprising providing two photo sensors adapted to sense the metal at entry and exit of the group and if the front of metal does not come out in predetermined time then operating the double strand snap shear along with flying shear;
controlling the cobble for reducing the amount of cobbte in the small looper area comprising providing two photo sensors adapted to Sense the metal at entry and exit of the group and if the front of metal does not come out in predetermined time then operating only the flying shear;
controlling, the cobble for,reducing the amount of cobble in the big looper area comprising providing two photo sensors adapted to sense the metal at entry and exit of the group and if the front of metal does not come out in predetermined time then operating only the flying shear.
17

9. A method for on-line contact-less automatic sensing of the cobbles in narrowly spaced
four strands of wire rod mill of steel plant using the system as claimed in anyone of claims 1
to 8.
18
10. An on-line contact-less automatic system for sensing the cobbles in narrowly spaced
strands of wire rod mill of steel piant substantially as herein described and illustrated with
reference to the accompanying figures 1 and 2.

A low cost, on-line contact-less automatic system for sensing and reducing the amount of cobbles by means of microprocessor based control. The sensing of metal/cobble is carried out selectively by photosensors(PS) and load current sensors(CS) located in selective positions for each metal strand in different rolling stands. In particular, the photosensor based control is provided in roughing stand (RS) and the 1st and 2nd intermediate(FIS & SIS) stand for sensing the cobbles in narrowly spaced four strands and suitable motor load current sensors utilized for sensing the rolled metal strands in the finishing stand. The system also provides for immediate action to prevent further accumulation of cobbled metal in narrowly spaced different strands by timely operation of appropriate flying and snap shears (DSSS or SSSS) such that mill availability is increased and production is increased resultantly by about 4%, with pay back of less than a week. Thus the present system of detecting and reducing the amount of metal cobble in wire rod mill, ensuring -safety of operators has high potential for industrial application and economic advantage.